1. Field of the Invention
The present invention relates to a mask inspection apparatus, a mask inspection method, and an electron beam exposure system, which inspect an electron beam exposure mask.
2. Description of the Prior Art
In lithography processes for semiconductor integrated circuits and the like, patterns formed on masks are exposed to light and transferred onto wafers. If a mask has a defect, the shape and the like of a pattern transferred onto a wafer becomes abnormal. Accordingly, the mask needs to be inspected.
Heretofore, a pattern of an exposure mask has been inspected by making a comparison with a predetermined reference image using an optical microscope or making a comparison between actual image data on the mask pattern observed using an SEM or the like and a predetermined reference image.
Further, Japanese Unexamined Patent Publication No. 2001-227932 discloses a technique for performing an inspection by applying a converged electron beam to a mask, converting the electron beam passed through the mask into light, and converting an optical image obtained by conversion to light into an image signal using a CCD camera to obtain an image of the mask.
Incidentally, in the case where an exposure mask is inspected using a microscope or the like, the exposure mask is detached from an electron beam exposure system, set on the microscope or the like, and then inspected. Accordingly, an inspection process takes a long time, and there is a risk of damaging the mask when the mask is detached or mounted or a risk of allowing dusts and the like to adhere to the mask.
Moreover, the method disclosed in Japanese Unexamined Patent Publication No. 2001-227932, a mask is inspected using a dedicated mask inspection apparatus. The mask cannot be inspected in the state where the mask is attached to an electron beam exposure system. Thus, there are similar problems such as damage to the mask and the contamination of the mask.